WASHINGTON (CNN) --The space shuttle program will resume "when we are fit to fly," which could mean delaying the announced goal of a launch next spring, NASA Administrator Sean O'Keefe said Wednesday.

But the agency is dedicated to implementing the recommendations of the independent panel that investigated the Columbia disaster and returning the remaining shuttles to flight, he said.

"We pledged to the Columbia families that we would find the problem, fix it, and return to the exploration objectives that their loved ones dedicated their lives to," O'Keefe said in a news conference.

"The board's efforts and the report we received yesterday completes the first of those commitments."

The Columbia Accident Investigation Board Tuesday released a 248-page report that includes 29 separate recommendations for changes, ranging from better camera views of each shuttle launch to better controls for how unwanted items like waste paper are handled near the shuttle.

It also recommended institutional changes to make the NASA bureaucracy more safety conscious.

"The very first important step is to accept those findings and comply with the recommendations, and that is our commitment. We intend to do that without reservation," O'Keefe said.

NASA is hoping to launch a shuttle mission sometime between March 11 and April 6. Many outside experts are saying that is unlikely to happen, and NASA officials have said the date could easily slip if anybody believes there's a problem.

"We'll see," O'Keefe said about the goal. "From the technical hardware standpoint there are a number of options that would permit an opportunity to [launch in the spring].

The larger questions that deal with some of the management systems -- the culture of how we do business -- we need to set the bar higher than [the Columbia accident board] did."

He added, "The standards we are expecting of ourselves, we need to be our toughest critics on that. Those are going to be more difficult to assess in terms of a calendar or timeline. I think it's going to be a case of when we are fit to fly. That's when it's going to occur."

A 27-member blue-ribbon panel of ex-astronauts, engineers, scientists, managers, and a sociologist has been picked to ensure that NASA meets the intent of all of the accident board's recommendations.

Columbia broke up February 1 on re-entry over Texas, just 16 minutes before its planned landing after finishing a successful 16-day science mission. All seven astronauts were killed.